Since C++17, using template specialization 'std::allocator<void>' in any shape or form (even just mentioning it) is deprecated! A simple workaround is replacing 'void' by another (preferably empty) type, e.g. 'fmt::monostate'.

Found by Clang 9 in Visual Studio.

Name hiding.
Signed-off-by: Daniela Engert <dani@ngrt.de>

C++17 deprecated 'std::result_of' in favour of 'std::invoke_result' and will ban it outright in C++20. Therefore
- implement 'internal::result_of' in terms of 'std::invoke_result' when compiling C++17 mode.
- implement 'internal::result_of' in terms of 'std::result_of' when compiling in modes C++11 or C++14.
Signed-off-by: Daniela Engert <dani@ngrt.de>

Howard Hinnant's 'date' library recently gained these two new formatting specifiers. This implementation in {fmt} includes support for 'std::chrono::duration' specializations with floating-point representation types and user-definable precision.
Signed-off-by: Daniela Engert <dani@ngrt.de>

The formatting syntax follows p1361r0, augmented by a precision field as proposed in #1004.
Signed-off-by: Daniela Engert <dani@ngrt.de>

Mostly equivalent to 'sprintf(const S &format, const Args & ... args)' but generates at most 'n' characters through output iterator 'it'. The output type is the same as with 'format_to_n'.
Signed-off-by: Daniela Engert <dani@ngrt.de>

These problems are pointed out by clang-tidy and fail compilation on msvc at /W4 /WX.
Signed-off-by: Daniela Engert <dani@ngrt.de>

This reverts commit 4a059914.